The Kempner Power Wagon Museum

Technical support


QUESTION: How Do I Remove Broken Manifold Bolts?  I have not had success in the past using easy-outs.

Normally, there are no bolts holding the manifold assembly to the engine block.  The manifolds are mounted on heat treated studs using thirteen seize-proof nuts.  You should be able to remove the manifolds by taking off those nuts and not disturbing the studs in the block.  Some studs go into the water jacket.  Occasionally, a stud seems to have more grip on the nuts than on the engine block.  This can result in the studs coming out so drain the coolant before removing any stud. 

If at all possible, do not separate the intake manifold from the exhaust manifold. There is a high probability that bolts holding them together will break.  The casting is thin at the threaded holes for these bolts and it is not unusual for the casting to break.  If the gasket between them has deteriorated, you can use various fillers such as J.B.Weld or high temperature gasket cement.  More on dealing with one of these bolts below.


The following image lists the correct studs, washers, and nuts.

manifold.jpg (380276 bytes)

You are right about easy-outs. They break off or they work like a tapered reamer to destroy the threads in the block. And there's no drilling out the remains of a broken easy-out. I have had great success (for me that means it worked each time) using reverse twist drills available from Eastwood or Harbor Freight. Preparation is critical.

You cannot rush this. Soak the broken studs in penetrating oil for several days prior to the day you drill. I have five brands in my shop - Pennzoil seems best for this. Then, if the engine is still in the truck, remove everything that is in the way because the drill must be perfectly aligned. Working in an uncomfortable posture will affect your patience.

DO NOT USE PENETRATING OIL NOW! Use a center punch and be sure the drill is centered. Drill slowly so the bit has a chance to catch. I start with a small bit to make a good pilot hole and then go to successively larger sizes. Check your drill bit in a hole with the stud removed to be sure the bit has adequate clearance so it will not damage the threads in the block. Do not use the size drill specified for tapping that size thread. That size drill actually is larger than the finished hole.  During threading, some metal is displaced toward the center of the hole (the section of the thread that goes deepest in the "vee" of the thread on the stud.  If your hole is centered and aligned, your best case is that the broken stud backs out on the drill bit. Second best is you get a thread "spiral" you can "pick" out.

Worst case is you have a hole that careful use of the correct tap will clean out for reuse. Do not force the tap. Check to be sure it has started in existing threads. Eighth turn forward, then back. Use penetrating oil since there's still a rust bond to overcome. This is a slow and deliberate process. If you are impatient, you might as well take a sledge hammer and break the block around the studs to get them out.


Here's a procedure for dealing with a broken bolt that holds the manifold sections together.  Those may be the most difficult bolts to repair on the whole truck. The old bolts are much harder than the manifold and a drill typically will want to go along side the bolts. This is a "Be Patient" situation.

Normally, you have been left with a bolt remnant that has broken off unevenly. If the remnant extends beyond the manifold, it is reasonable that you have already attacked it with the Vice Grips. Before you mutilate it totally, cut it off and grind the remnant parallel to the face of the manifold. This gives you a flat surface perpendicular to the drill. You may be able to make a center punch mark to use for drilling. The operative word here is CENTER.

At this point, I must remind you to have a SHARP drill bit, plenty of light, and safety glasses - prescription if you wear them.

Use a good drill press with a table that clamps securely. You are not good enough to do this with a hand held drill. No one is.

Use a vice on the drill press table to hold the manifold so it DOES NOT MOVE.

Adjust the table so the drill chuck is close to the manifold. This minimizes the free play in the drill.

Use a short drill so it cannot flex and seek its own path along side the bolts.

If you have a good bolt remnant with a good center punch mark, proceed carefully.  Do not force the drill.  Back it out often to clean out the drilled hole.

If the bolt broke off below the surface of the manifold, getting the drill bit centered is almost impossible. Some machine shops have drill guides that fit into the hole and center the drill.

If the remnant is broken off below the surface and you do not have access to a drill guide, you can try to create a center punch mark by using a punch with a diameter that matches the size of the hole.   If you are successful in making the center punch mark, proceed as above.

If you cannot establish a center punch mark,  Bring the drill bit down until it just makes contact with the end of the broken bolt.  Let it turn there so the cutting edges can create its own indentation in the end of the bolt.  You will be able to see if the drill bit is diverted away from center.

Some of you may have access to a bit that is cut like a milling tool.  It would cut away any uneven part of the broken bolt and let you have that perpendicular face for drilling. 

All the above procedures have the goal of removing most of the metal of the broken bolt and leaving a hole that can have the original threads cleaned out and reused.  All these procedures have little benefit if you cut new threads since the new threads can cut away the old threads and leave no "teeth" for the replacement bolt to get hold of. 

Patience and Good Luck.